Pole-shoe for dynamo-electric machines.



- No. 72 3,989. PATENTED MAR, 31, 1903.

A. GHURCHWARD. POLE SHOE FOR DYNAMO ELECTRIC MACHINES.

APPLICATION FILED AUG. 23, 1901.

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Inventor A lexcmder Churchward.

WLtnesses.

UNITED STATES PATENT OFFICE.

ALEXANDER OHURCHWARD, OF CHICAGO, ILLINOIS, ASSIGNOR TO GEN- ERAL ELECTRIC COMPANY, "A CORPORATION OF NEW YORK.

POLE-SHOE FOR DYNAMO-ELECTRLC MACHINES.

SPECIFICATION forming part of Letters Patent No. 723,989, dated March 31, 1903.

Application filed August 23, 1901. Serial No'. 73 049. (No model.)

To all whom it may concern:

Be it known that I, ALEXANDER CHURCH- WARD, a citizen of the United States, residing at Chicago, county of Cook, State of Illinois, have invented certain new and useful Improvements in Pole-Shoes for Dynamo-Electric Machines, (Case No. 2,133,) of which the following is a specification.

This invention relates-to dynamo-electric machines; and its object is to insure a more even distribution of the lines of force induced by the field-magnets, and thus prevent sparking at the brushes. It is Well known that ordinarily the rotation of the armature tends to crowd the lines of force in the fie1d toward that side of the field-pole from which the armature is moving, a result which interferes with the eificiency of the machine. It is customary in some machines to overcome this objection to a certain degree by slotting the fie1d-magnet core on a plane transverse to the line of movement of the armature; but such machines generally have also a pole-shoe in order that as many lines of force as possible may be utilized. Such a construction is shown in the United States Patent to Short, No. 607,609. The efiect of the slot is reduced almost to a minimum by the shoe, because the latter completely encircles the end of the magnet-core or pole-piece, so that there is a metallic path for the magnetic flux from one side of the pole to the other.

My invention consists in a pole-shoe slotted like the pole-piece to interpose the same airgap in the shoe as in the pole-piece, and thus cause both to work to their full effectiveness.

In the accompanying drawings, Figure 1 is a side elevation of a portion of a multipolar machine embodying myinvention. Fig. 2 is an end view of one of the pole-pieces, showing the slotted shoe.

The pole-piece A is provided with the usual slot a, radial to the armature and parallel with the axis of rotation. The pole-shoe B is made in two U-shaped parts, which terminate at the slot 0., so that the continuity of the shoe is interrupted at that point, as it does not magnetically bridge the slot. It is evident that the shoe could be pieced out across the slot with some non-magnetic material, if this should be found desirable for mechanical rea sons.

What I claim as new, and desire to secure by Letters Patent of the United States, is-= 1. A pole-shoe which only partially encircircles the pole-piece.

2. A pole-shoe Whose magnetic continuity is interrupted. I

3. The combination with a slotted polepiece, of a pole-shoe which does not magnetically bridge said slot.

4. The combination with a slotted polepiece, of .a pole-shoe which ends at the edge of the slot.

5. The combination with a slotted polepiece, of a pole-shoe made in two U-shaped parts, each of which partially encircles the pole-piece and terminates at said slot.

In witness whereof I have hereunto set my hand this 19th day of August, 1901. H

ALEXANDER OHURGHWARD.

Witnesses:

BENJAMIN B. HULL, J. SORIBNER. 

